When Mrs Secure Sliced Through The Hedgetrimmer Flex...

[securespark]

...what happened to the protective devices?
(In the circuit were a 1362 13A fuse followed by a 3871 B32 breaker and finally a 4293 63A 30mA RCD)

 

[flyingsparks]

All 3 went?

 

[Lectrician]

I reckon the B32.

 

[EFLImpudence]

Nothing.

I did think that was what you meant by the question.

 

[RF Lighting]

Counter intuitive but it looks like it'll have been the RCD

 

[KingboyD]

You're whole house went off so the 63A 30mA RCD

 

[OwainDIYer]

service fuse blew.

Everything else intact. (including Mrs Secure I hope)

 

[JohnW2]

...what happened to the protective devices?
(In the circuit were a 1362 13A fuse followed by a 3871 B32 breaker and finally a 4293 63A 30mA RCD)

As I think I reported at the time, the last time I did this (with essentially the same protective devices in circuit), it was (only) the B32 that operated. The time before that (yes, I know I should be more careful ), none of the devices operated.

Kind Regards, John

 

[DetlefSchmitz]

Yeah, just the B32.

 

[securespark]

EFLI got there first.

Yup, nothing...

 

[ban-all-sheds]

Do you think it would have been any different if the flex had had an earthed core in it?

 

[ultomoat]

(In the circuit were a 1362 13A fuse...

Did I miss something or was the wrong fuse fitted? Surely a hedge trimmer is less than 1000w?

 

[JohnW2]

Do you think it would have been any different if the flex had had an earthed core in it?

As we've often discussed, quite possibly (and, as you know, I am a great believer in 3-core flex for such tools). However, even with an earth core, the duration of contact between one of the live cores and earth could be a fairly small fraction of a cycle, and I don't know how likely an RCD is to operate with such a transient earth fault - do you?

Kind Regards, John

 

[flyingsparks]

I should look more closely next time.. I thought that flex did have an earth core!

 

[JohnW2]

EFLI got there first. Yup, nothing...

... like my penultimate experience, then

As I've just written in terms of RCDs, and I think the same is true of OPDs, I personally know little/nothing about the duration of a fault (earth fault or over-current, respectively) required for a protective device to operate - does anyone? In the case of a fuse, I would guess/assume that if the duration of the over-current is appreciably less than the time it would take that current to cause the fuse to operate, then it probably won't operate. However, I don't really know in relation to RCDs and MCBs.

Kind Regards, John